Internet Engineering Task Force (IETF)
Request for Comments: 6162
Updates: 5959
Category: Standards Track
ISSN: 2070-1721
S. Turner
April 2011

Elliptic Curve Algorithms for Cryptographic Message Syntax (CMS)

Asymmetric Key Package Content Type


This document describes conventions for using Elliptic Curve cryptographic algorithms with SignedData and EnvelopedData to protect the AsymmetricKeyPackage content type. Specifically, it includes conventions necessary to implement Elliptic Curve Diffie-Hellman (ECDH) with EnvelopedData and Elliptic Curve Digital Signature Algorithm (ECDSA) with SignedData. This document extends RFC 5959.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at

Copyright Notice

Copyright © 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

1. Introduction

[RFC5959] describes conventions necessary to protect the AsymmetricKeyPackage content type [RFC5958] with Cryptographic Message Syntax (CMS) protecting the following content types: SignedData [RFC5652], EnvelopedData [RFC5652], EncryptedData [RFC5652], AuthenticatedData [RFC5652], and AuthEnvelopedData [RFC5083]. This document amends [RFC5959] by extending the algorithms used with SignedData and EnvelopedData to include Elliptic Curve Digital Signature Algorithm (ECDSA) and Elliptic Curve Diffie- Hellman (ECDH), respectively. Familiarity with [RFC5959] and [RFC5753] is assumed.

This document does not define any new algorithms; instead, it refers to previously defined algorithms.

1.1 Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

2. AsymmetricKeyPackage

As noted in Asymmetric Key Packages [RFC5958], CMS can be used to protect the AsymmetricKeyPackage. The following provides guidance for SignedData [RFC5652] and EnvelopedData [RFC5652] when used with Elliptic Curve algorithms.

2.1. SignedData

If an implementation supports SignedData, then it MAY support ECDSA [RFC6090][RFC5753].

2.2. EnvelopedData

When key agreement is used, standard (as opposed to cofactor) ECDH [RFC6090][RFC5753] MAY be supported.

3. Public Key Sizes

The easiest way to implement SignedData and EnvelopedData is with public key certificates [RFC5280][RFC5480]. If an implementation supports ECDSA or ECDH, then it MUST support keys on the P-256 curve.

4. Security Considerations

   The security considerations from [RFC5280], [RFC5480], [RFC5652],
   [RFC5753], [RFC5959], and [RFC6090] apply.

5. References

5.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.
   [RFC5480]  Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
              "Elliptic Curve Cryptography Subject Public Key
              Information", RFC 5480, March 2009.
   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, September 2009.
   [RFC5753]  Turner, S. and D. Brown, "Use of Elliptic Curve
              Cryptography (ECC) Algorithms in Cryptographic Message
              Syntax (CMS)", RFC 5753, January 2010.
   [RFC5958]  Turner, S., "Asymmetric Key Packages", RFC 5958, August
   [RFC5959]  Turner, S., "Algorithms for Asymmetric Key Package Content
              Type", RFC 5959, August 2010.
   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
              Curve Cryptography Algorithms", RFC 6090, February 2011.

5.2. Informative Reference

   [RFC5083]  Housley, R., "Cryptographic Message Syntax (CMS)
              Authenticated-Enveloped-Data Content Type", RFC 5083,
              November 2007.

Author's Address

Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031